Such electrodes can be made by impregnating a three-dimensional porous support with an active mass in the form of a paste made by the active material proper being fed into a gel based on a hydroxycolloid such as carboxy methyl cellulose (CMC) or hydroxy propyl methyl cellulose (HPMC). By coating the support and drying the paste, it is possible to obtain a finished electrode structure which can used directly in a cell. The advantage of that type of method lies in the fact that a three-dimensional porous support can be impregnated in a single step, whereas in the prior method of filling a conventional sintered nickel support, impregnation had to be performed in several successive steps in order to fill the support with the right amount of active mass.
However, the method recommended above suffers from implementation difficulties essentially related to the viscosity of the paste during the filling and drying steps. Although hydroxycolloids used up until now give the paste a viscosity well suited to filling, they do not enable the paste to be then held correctly in the support.
An aim of the present invention is to avoid this drawback, and to provide an active mass which is easier to use than known active masses.